1. Field of the Invention
This invention relates generally to the field of treating wells to stimulate fluid production. More particularly, the invention relates to the field of abrasive jet perforating in oil and gas wells.
2. Description of the Related Art
Abrasive jet perforating (AJP) uses fluid slurry pumped under high pressure to perforate tubular goods around a wellbore, where the tubular goods include tubing, casing, and cement. Since sand is the most common abrasive used, this technique is also known as sand jet perforating (SJP). Abrasive jet perforating was originally used to extend a cavity into the surrounding reservoir to stimulate fluid production. It was soon discovered, however, that abrasive jet perforating could not only perforate, but cut (completely sever) the tubular goods into two pieces. Sand laden fluids were first used to perforate and cut well casing in the 1930's.
Abrasive jet perforating was eventually attempted on a commercial scale in the 1960's. While abrasive jet perforating was a technical success (over 5,000 wells were treated), it was not an economic success. The tool life in abrasive jet perforating was measured in only minutes and fluid pressures high enough to cut casing were difficult to maintain with pumps available at the time. A competing technology, explosive shape charge perforators, emerged at this time and offered less expensive perforating options.
Consequently, very little work was performed with abrasive jet perforating technology until the late 1990's. Then, more abrasive-resistant materials used in the construction of the perforating tools and jet orifices provided longer tool life, measured in hours or days instead of minutes. Also, advancements in pump materials and technology enabled pumps to handle the abrasive fluids under high pressures for longer periods of time. The combination of these advances made the abrasive jet perforating process more cost effective. Additionally, the use of coiled tubing to convey the abrasive jet perforating tool down a wellbore has led to reduced run time at greater depth. Further, abrasive jet perforating does not require explosives and thus avoids the accompanying danger involved in the storage, transport, and use of explosives. However, the basic design of conventional abrasive jet perforating tools used today has not changed significantly from those used in the 1960's.
Abrasive jet perforating tools and casing cutters were initially designed and built in the 1960's. There were many variables involved in the design of these tools. Some tool designs varied the number of jet locations on the tool body, from as few as two jets to as many as 12 jets. The tool designs also varied the placement of those jets, such, for example, positioning two opposing jets spaced 180° apart on the same horizontal plane, three jets spaced 120° apart on the same horizontal plane, or three jets offset vertically by 30°. Other tool designs manipulated the jet by orienting it at an angle other than perpendicular to the casing or by allowing the jet to move toward the casing when fluid pressure was applied to the tool.
Abrasive jet perforating tools are typically sized appropriately for the casing. Occasionally a centralizer is used with the tool to keep it from touching the low side of the casing. Abrasive jet perforating tools typically have a uniform outer diameter, with the exception of the mounting location for the jets.
An important concern for abrasive jet perforating tools is protecting them from the damage caused by the splash back of the pressurized abrasive fluid. This splash back can cut tool components as easily as it cuts the target tubing. Greater resistance to damage from this splash back translates into increased run time and life for the tool while downhole. The demand is high for numerous sets of perforations to be performed in one trip downhole as many different treatment stages may be employed.
Another challenge for abrasive jet perforating is creating a hole or window in the casing that is larger than the hole naturally created by the spraying fluid. The traditional threaded jet configuration is limited by its size to the proximity of spacing between the abrasive jets. For example, a tool has been built to create vertical slots that moves to connect its holes because the abrasive jets cannot be placed close enough together to allow them to cut a slot simultaneously. Alternatively, situations that require a casing window may need a large circle or oval shape for their processes.
The following patents and publications are representative of conventional abrasive jet perforating and cutting tools, along with apparatuses and methods that may be employed with the tools.
U.S. Pat. No. 3,130,786 by R. W. Brown et al., “Perforating Apparatus”, Apr. 28, 1964, discloses an abrasive jet perforating tool. The tool comprises a cylindrical conduit for abrasive fluid to be pumped through and jet nozzles laterally extending from the conduit to direct the abrasive fluid through the casing into the surrounding formation. Factors such as the pressure differential and the ratios of the diameter of the nozzle orifice to the length of the nozzles and to the size of the abrasives are kept within predetermined limits for optimum penetration.
U.S. Pat. No. 3,145,776 by F. C. Pittman, “Hydra-Jet Tool”, Aug. 25, 1964, discloses protective plates for an abrasive jet perforating tool. The plates, made of abrasive resistant material, are designed to fit flatly to the body of the tool around the perforating jets. The plates are employed to protect the body of the tool from ejected abrasive material that rebounds. The protective plates disclosed in Pittman are not designed to protect the abrasive jets themselves.
U.S. Pat. No. 3,266,571 by J. C. St. John et al., “Casing Slotting”, Aug. 16, 1966, discloses an abrasive jet perforating tool designed to cut slots of controlled length. The slot lengths are controlled by abrasive resistant shields attached to the tool to block the flow from rotating abrasive jets.
U.S. Pat. No. 4,050,529 by K. M. Tagirov et al., “Apparatus for Treating Rock Surrounding a Wellbore”, Sep. 27 1977, discloses an abrasive jet tool for successively perforating and then fracturing reservoirs. The nozzles of the abrasive jets are designed to snugly fit against the casing to allow perforating at one pressure immediately followed by fracturing at a higher pressure.
U.S. Pat. No. 5,499,678 by J. B. Surjaatmadja et al., “Coplanar Angular Jetting Head for Well Perforating”, Mar. 19 1996, discloses a jetting head for use in an abrasive jet perforating tool. The jet openings in the jetting head are coplanar and positioned at an angle to the longitudinal axis of the tool. The angle is chosen so that the plane of the jet openings is perpendicular to the axis of least principal stress in the formation being fractured. The tool must be custom-made for each job, since the entire jet head is angled into the tool.
U.S. Pat. No. 5,765,756 by G. D. Jorden et al., “Abrasive Slurry Jetting Tool and Method”, Jun. 16, 1998, discloses an abrasive jet perforating tool with telescoping jetting nozzles. The jetting nozzles are operated perpendicularly to the longitudinal axis of the tool body, although the nozzle assemblies can pivot back into the tool body for retrieval back up the wellbore. The Jordan et al. patent discloses using the perforating tool for removing a casing section, cutting a window, series of longitudinal slots, or plurality of perforations in a wellbore casing, and removing or cleaning a wellbore formation to enhance perforation.
U.S. Pat. No. 7,159,660 B2 by D. M. Justus, “Hydrajet Perforating and Fracturing Tool”, Jan. 9, 2007, discloses an abrasive jet perforating and fracturing tool. The tool comprises both abrasive jet ports and fracturing ports having larger apertures than the jet ports. The fracturing ports are used to eject fracturing fluid into the formation at a faster rate than possible through the jet ports. The tool further comprises a rotating sleeve, turned by a power unit, with apertures that align or misalign with the jet ports and control ports to control flow through the ports.
U.S. Pat. No. 7,497,259 B2, by L. J. Leising et al., “System and Method for Forming Cavities in a Well”, Mar. 3, 2009, discloses a downhole assembly string for perforating wells. The string comprises an anchoring mechanism, a multi-cycle vertical incrementing tool, a swivel orienting device and a perforation tool, suspended from coiled tubing. The perforation tool is moved vertically by the incrementing tool, which is activated by fluid pressure changes.
An SPE publication by J. S. Cobbett, “Sand Jet Perforating Revisited”, SPE 55044, SPE Drill. & Completion, Vol. 14, No. 1, p. 28-33, March 1999, discloses the use of sand jet perforating (abrasive jet perforating) with coiled tubing to increase production in damaged wells, using examples of neglected wells in Lithuania.
A publication by Gensheng Li et al., “Abrasive Water Jet Perforation—An Alternative Approach to Enhance Oil Production”, Petroleum Science and Technology, Vol. 22, Nos. 5 & 6, p. 491-504, 2004, discloses laboratory results and field tests showing the effects of different parameters on the ability of abrasive water jet perforating (abrasive jet perforating) to improve well performance and the mechanism by which it works.
Halliburton Document HO4903, “Hydra-Jet Perforating Process Service” September 2006 discloses an abrasive jet perforating tool and process. The perforating tool is conveyed by coiled tubing to allow access to deviated or horizontal wellbores, damaged casing, or other tight restrictions.
SPE publication by S. W. Loving et al., “Abrasive Cutting Technology Deployed Via Coiled Tubing”, SPE 92866, SPE/ICoTA Coiled Tubing Conference and Exhibition, April 2005, discloses an abrasive jet cutting tool for cutting production tubing, drill pipe, drill collars, completion components, and casing strings. The cutting tool is deployed using conventional coiled tubing and is rotated by pumping an abrasive slurry through a downhole sealed bearing, positive displacement motor mounted above an abrasive cutting head. The abrasive slurry is pumped down the coiled tubing by a conventional high pressure pump.
SPE publication by B. W. McDaniel et al, “Use of Hydrajet Perforating To Improve Fracturing Success Sees Global Expansion” SPE 114695, CIPC/SPE Gas Tech. Symposium June, 2008, discloses the history of hydrajet-assisted fracturing (HJAF), the use of abrasive jet perforating in conjunction with hydraulic fracturing. The combination of hydrajet perforating and hydraulic fracturing can increase well production while reducing well costs over previous stimulation methods.
Thus, a need exists for an abrasive jet perforating tool and method of use that can provide better protection around the installation locations of the jet orifices and can be used in pipe with a small inner diameter.